Energetic constituent for incendiary and explosive compositions

ABSTRACT

AN ENERGETIC CONSTITUENT FOR INCENDIARY AND EXPLOSIVE COMPOSITIONS COMPRISING LIQUID NON-EXPLOSIVE ORGANIC NITRATE, FOR EXAMPLE ISOPROPYL NITRATE, THICKENED WITH NITROCELLULOSE AND ETHYL OR METHYL CENTRALITE. THIS CONSTITUENT MAY BE USED, FOR EXAMPLE, AS THE SENSITISING INGREDIENT IN AQUEOUS SLURRY EXPLOSIVE AND IN EXTRUDABLE GELATINOUS BLASTING AND IN POWDERED AMMONIUM NITRATE BLASTING EXPLOSIVES.

United States Patent Olfice 3,684,595 Patented Aug. 15, 1972 3,684,595 ENERGETIC CONSTITUENT FOR INCENDIARY AND EXPLOSIVE COMPOSITIONS William Allan Craig, Glasgow, and Owen Allen Gurton,

Fairlie, Scotland, assignors to Imperial Chemical Industries Limited, London, England No Drawing. Filed Apr. 7, 1970, Ser. No. 26,414 Claims priority, application Great Britain, Apr. 25, 1969, 21,313/69 Int. Cl. C06b 15700 US. Cl. 149-41 14 Claims ABSTRACT OF THE DISCLOSURE An energetic constituent for incendiary and explosive compositions comprising liquid non-explosive organic nitrate, for example isopropyl nitrate, thickened with nitrocellulose and ethyl or methl centralite. This constituent may be used, for example, as the sensitising ingredient in aqueous slurry explosive and in extrudable gelatinous blasting and in powdered ammonium nitrate blasting explosives.

This invention relates to an energetic constituent for incendiary and explosive compositions, to a method for preparing such constituent and to incendiary and explosive compositions comprising such constituent.

Liquid non-explosive organic nitrates, for example alkyl nitrate such as isopropyl nitrate and amyl nitrate, are known energetic and sensitising constituents of incendiary compositions and propellent and blasting explosive compositions. In blasting explosives, for example, they are especially advantageous because, in certain compositions, their use renders the use of a self-explosive sensitising ingredient unnecessary. Explosive compositions comprising liquid non explosive organic nitrates as a sensitising ingredient are described in our co-pending United Kingdom patent application No. 18,831/68.

Hitherto, the liquid non-explosive organic nitrates have tended to segregate from the other ingredients of incendiary and explosive compositions unless effectively thickened and it is an object of this invention to provide a thickened liquid non-explosive organic nitrate for use as an energetic constituent of incendiary compositions and propellent and blasting explosive compositions. We have now discovered that liquid non-explosive organic nitrate can be advantageously thickened to a clear, consistent gel which exhibits little or no syneresis by mixing it with nitrocellulose and ethyl or methyl centralite (diethyl diphenylurea or dimethyl diphenylurea).

Thus in accordance with this invention an energetic constituent for incendiary and explosive compositions comprises liquid non-explosive organic nitrate thickened with nitrocellulose and ethyl or methyl centralite.

The preferred organic nitrates are aliphatic mononitrates having from 3 to 8 carbon atoms. The preferred organic nitrates include n-propyl nitrate, isopropyl nitrate and amyl nitrate.

Preferably the nitrocellulose has a nitrogen content of 11.5 to 12.5% by weight and is such that a solution containing cc. of water has a viscosity of at least 50 poises at 20 C. The nitrocellulose may be used dry but it is uusally safer to use nitrocellulose wetted with water or industrial methylated spirit.

The nitrocellulose and centralite are preferably each present in an amount of 1 to 5% by weight of the liquid non-explosive organic nitrate and it is preferred that the weights of nitrocellulose and centralite should be approximately equal.

The thickened liquid non-explosive organic nitrate is advantageously prepared by suspending the nitrocellulose in the organic nitrate and adding the ethyl or methyl centralite, but, if desired, in the preparation of compositions containing additional ingredients, the nitrocellulose or the centralite, or both, may be incorporated in the additional ingredients before the addition of the organic ni trate. For example, in compositions containing water it is an advantageous safety precaution to add the nitrocellulose as a slurry in the water.

In accordance with a further aspect of the invention an incendiary or explosive composition comprises the aforedescribed energetic constituent. For example, an extrudable gelatinous blasting explosive which is readily initiated and propagates reliably in small diameters may be prepared using liquid non-explosive organic nitrate as the sole sensitising liquid, no self-explosive ingredient being required to ensure propagation. Such an extrudable composition advantageously comprises (by weight) 18 to 40% liquid non-explosive organic nitrate, 0.2 to 2.0% nitrocellulose, 0.2 to 2.0% ethyl or methylcentralite, 60 to ammonium nitrate and 0 to 10% sodium nitrate. These compositions are of uniform consistency and the liquid organic nitrate does not separate on storage.

Aqueous slurry explosives capable of propagation in small diameters may also be prepared using the thickened liquid non-explosive organic nitrate of the invention as the sole sensitising ingredient. Preferred slurry compositions of the invention comprise (by weight) 10 to 30% liquid non-explosive organic nitrate, 0.1 to 1.5% of nitrocellulose, 0.1 to 1.5 of ethyl or methyl centralite, 5 to 15% water, 40 to 65% ammonium nitrate, 0 to 20% sodium nitrate, and 0 to 20% aluminium. Water-thicken ing agents, for example guar, gum, with, if desired, a cross-linking agent therefor, for example Zinc chromate, may also be advantageously incorporated in the slurry composition. The organic nitrate does not separate from the slurry. Aqueous slurries of the invention containing no self-explosive ingredient will propagate detonation when confined under pressures of at least up to 1-00 p.s.i. which is a property not possessed by any practical slurries hitherto made without a self-explosive ingredient.

Ammonium nitrate powdered explosives may also advantageously incorporate the thickened liquid non-explosive organic nitrate of the invention as the sensitising fuel. Preferred ammonium nitrate powdered explosive compositions of the invention comprise (by weight) 7 to 17% liquid non-explosive organic nitrate, 0.07 to 0.5% nitrocellulose, 0.07 to 0.5% of ethyl or methyl centralite and 80 to 92% of ammonium nitrate.

The explosive compositions of the invention are very insensitive to ignition by friction and impact and are consequently safer in manufacture and use than conventional explosives incorporating self-explosive ingredients.

The invention is further illustrated by the following examples in which all parts and percentages are by weight.

In the examples a fibrous nitrocellulose having an average nitrogen content of 12.0 to 12.3% nitrogen was used. A solution containing 3 grams of this nitrocellulose dissolved in 95 cc. of acetone and 5 cc. of water had a viscosity of poises at 20 C. The nitrocellulose was used water-wet with 30% of water but the amounts quoted are the weights as dry.

The ammonium nitrate used in Examples 1, 4 and 5 was granular ammonium nitrate of particle size such that 100% passed a B.S. 16 mesh sieve, 60% passed a B.S. 60 mesh sieve and 5% passed a B.S. mesh sieve. In Examples 2 and 3 a coarse grade of ammonium nitrate was used which was such that 90% passed a B.S. 10 mesh sieve and 30% passed a B.S. 30 mesh sieve.

3 EXAMPLE 1 The explosive composition of this example was an extrudable gelatinous explosive of the following composition:

Percent Isopropyl nitrate 20 Nitrocellulose 0.6 Ethyl centralite 0.6 Sodium nitrate 10.0 Ammonium nitrate 68.8

The explosive Was prepared by forming a mixed suspension of the nitrocellulose in the isopropyl nitrate, adding the ethyl centralite to form a clear gel and subsequently incorporating the ammonium nitrate and sodium nitrate into the gel.

This composition could be initiated by a detonator containing a base charge of 1.0 g. pentaerythritol tetranitrate (PETN). When initiated under confinement in a 3" diameter x A" thick mild steel tube by means of a g. Pentolite (50/50 PETN/TNT) primer it detonated with a velocity of detonation of approximately 5 km./sec. There was no tendency for the isopropyl nitrate to segregate from the other ingredients.

EXAMPLES 23 The explosive compositions of these examples were aqueous slurry explosives of the following compositions and properties:

Example Ingredients, percent: Isopropyl nitrate Wat P9595 HF'HP O s ps r' Ethyl centralite. Ammonium nitrate".

Aluminium (granular) Guar gum Zinc chromate Properties:

Minimum initiator (detonator base charge) Density, g./ml

V.O.D. 3 diameter in steel tube, m.p.s

1 1.0 g. PETN.

In the preparation of the compositions the nitrocellulose was slurried with water, the slurry was suspended in the isopropyl nitrate and the centralite was added to the suspension. The remaining ingredients were then mixed into the resulting gel.

There was no tendency for the isopropyl nitrate to segregate from the other ingredients of the slurries.

EXAMPLES 45 The explosive compositions of these examples were ammonium nitrate powdered compositions of the follow- In the preparation of these compositions the nitrocellulose was suspended in the isopropyl nitrate and the ethyl centralite was added to form a gel. The remaining ingredients were then mixed into the gel.

What We claim is:

1. An energetic constituent for incendiary explosive compositions, which constituent comprises liquid non-explosive aliphatic mononitrate having from 3 to 8 carbon atoms thickened with nitrocellulose and a compound selected from the group consisting of ethyl centralite and methyl centralite.

2. An energetic constituent as claimed in claim 1 wherein the aliphatic mononitrate has from 3 to 5 carbon atoms.

3. An energetic constituent as claimed in claim 1 wherein the organic nitrate comprises n-propyl nitrate, isopropyl nitrate and amyl nitrate.

4. An energetic constituent as claimed in claim 1 wherein the nitrocellulose has a nitrogen content of 11.5 to 12.5% by weight and is such that a solution containing 3 grams nitrocellulose dissolved in cc. of acetone and 5 cc. of water has a viscosity of at least 50 poises at 20 C.

5. An energetic constituent as claimed in claim 1 where in the nitrocellulose and centralite are each present in an amount of l to 5% by weight of the aliphatic non-explosive organic nitrate.

6. An energetic constituent as claimed in claim 1 Wherein the weights of nitrocellulose and centralite are approximately equal.

7. A method for the preparation of an energetic constituent for incendiary explosive compositions which constituent comprises a liquid non-explosive organic nitrate, said method comprising suspending the nitrocellulose in the organic nitrate and then adding the centralite to the suspension.

8. A method as claimed in claim 7 wherein nitrocellulose slurried in water is suspended in the organic nitrate.

9. An extrudable explosive composition comprising an energetic constituent as claimed in claim 1, said explosive composition comprising (by Weight) 18 to 40% of the liquid non-explosive organic nitrate, 0.2 to 2% nitrocellulose, 0.2 to 2.0% ethyl or methyl centralite, 60 to 80% ammonium nitrate and up to 10% sodium nitrate.

10. An aqueous slurry explosive composition comprising an energetic constituent as claimed in claim 1, said explosive composition comprising (by weight) 10 to 30% of the liquid non-explosive organic nitrate, 0.1 to 1.5% nitrocellulose, 0.1 to 1.5% ethyl or methyl centralite, 5 to 15% water, 40 to 65% ammonium nitrate, up to 20% sodium nitrate and up to 20% aluminium.

11. An aqueous explosive slurry composition as claimed in claim 10 comprising guar gum as a water-thickening agent.

12. A composition as claimed in claim 11 comprising a cross-linking agent to cross-link the guar gum.

13. A composition as claimed in claim 12 comprising zinc chromate as a cross-linking agent.

14. An ammonium nitrate powdered explosive composition comprising an energetic constituent as claimed in claim 1, said explosive composition comprising (by weight) 7 to 17% liquid non-explosive organic nitrate, 0.07 to 0.5% nitrocellulose, 0.07 to 0.5 ethyl or methyl centralite and 80 to 92% ammonium nitrate.

References Cited UNITED STATES PATENTS 3,097,123 7/1963 Lewis et a1 149-400 3,225,050 12/ 1965 Barth-Wehrenalp et al.

14988 X 3,347,903 10/1967 Smiley 149-88 X 3,376,174 4/1968 Napoly et a1 149-100 X 3,377,219 4/1968 Stiefel et al. 149-88 CARL D. QUARFORTH, Primary Examiner S. J. LECHERT, JR., Assistant Examiner US. Cl. X.R. 

